Preparation Of WC-Fe-Ni Cemented Carbide By Hot Oscillating Pressing Sintering And Research On Properties Optimization

Cemented carbide has the advantages of high strength,high toughness,high wear resistance,etc.,and is currently one of the most widely used materials in mining,cutting tools,geological survey and other fields.However,the hardness and toughness of traditional cemented carbide are contradictory,which has become a bottleneck restricting the high-end application of cemented carbide,and conventional preparation methods cannot solve this problem,so it is of great strategic and economic significance to find a new sintering technology for high-strength and high-toughness cemented carbide.In this paper,taking WC-Fe-Ni cemented carbide as the research object,metallographic microscopy,X-ray diffraction analysis,scanning electron microscopy,energy spectroscopy analysis,mechanical properties testing and other means were used to study the densification,microstructure and mechanical properties of WC-Fe-Ni cemented carbide prepared by hot oscillatory pressing sintering.The main findings are as follows:（1）The densification of hot oscillatory pressure sintered WC-Fe-Ni cemented carbide was studied,and it was found that with the progress of sintering,the influence of hot oscillating pressure on the densification of the specimen gradually increased,and the hot oscillating pressure promoted the particle rearrangement,grain boundary slip,plastic deformation and other mechanisms of the sintering process,which had a positive impact on the improvement of alloy densification.（2）When WC-Fe-Ni cemented carbide is sintered by hot oscillatory pressing at liquid phase sintering temperature,its density is 99.5%,the WC grain size is 0.58μm,the hardness and fracture toughness are 2052.1 MPa,15.48 MPa·m^1/2,and the comprehensive performance is better than that of the vacuum sintered sample.At the same time,it is found that the liquid phase is gradually filled into the powder pores during the liquid phase sintering process,which helps the elimination of pores and the uniform distribution of the bonding phase,and improves the mechanical properties of cemented carbide.（3）Under the same sintering temperature and holding time,the influence of the oscillatory sintering process（pressure amplitude and median pressure value）on the microstructure and properties of WC-Fe-Ni cemented carbide was studied,and it was found that with the increase of amplitude,the density of the specimen was higher,the grain size was finer,and the mechanical properties were better;with the increase of the median pressure,the density and mechanical properties of the specimen were increased,and the comprehensive performance of the sample was optimal when the HOP pressure was 40±5MPa,and its relative density was 99.17%.The grain size of WC is 0.62μm,the hardness is 1931 MPa,and the fracture toughness is 12.43 MPa·m^1/2.When the maximum pressure is the same,the oscillatory sintering has better comprehensive performance than the hot pressure sintering,and the density,hardness and fracture toughness of the material with a large pressure amplitude are also higher,and the pressure amplitude is the key parameter that determines the material performance.（4）In order to study the advantages of hot oscillatory pressure sintering,WC-Fe-Ni cemented carbide was prepared under the same sintering conditions by using hot oscillatory pressure sintering and hot pressure sintering,and it was found that compared with the hot pressure sintered specimen,the hot oscillatory pressure sintered specimen had a higher relative density,a smaller WC grain size and a narrower grain size distribution;in addition,the average free path of the bonding phase of the hot oscillatory pressure sintered specimen and the adjacency of the WC grains were also lower,and the tissue was more uniform and fine.Moreover,the hot oscillatory pressure sintered samples had higher hardness（2052.1 MPa）and fracture toughness(14.67 MPa·m^1/2),which were increased by 6.7%and 19.85%,respectively,compared with the hot press sintered samples.Hot oscillatory pressure promotes the flow of the liquid phase,affects the dissolution-re-precipitation process,thereby improving the densification of the alloy,the uniform distribution of the bonding phase,the increase of the WC/bonding phase interface,inhibiting the growth of WC grains,and improving the strength and toughness of the alloy.